1. Field of the Invention
The present invention relates to a memory readout system for a vehicle control device equipped with a built-in nonvolatile memory mounted to motor vehicles such as passenger vehicles and trucks, and in particular, relates to a memory readout system capable of reading out vehicle information and various data stored in a nonvolatile memory.
2. Description of the Related Art
A recent vehicle is equipped with a vehicle control device which is capable of performing an engine control operation and controlling operations of various vehicle devices mounted to a motor vehicle. It can be considered that such a vehicle control device is equipped with a built-in nonvolatile memory. Diagnosis information such as various types of error information (which will be referred to as the “dialogue information” through the specification) and diagnosis information are stored in the built-in nonvolatile memory. The dialogue information is read out from the built-in nonvolatile memory at a vehicle inspection. During a vehicle inspection, if a wrong or erroneous operation deletes the dialogue information stored in the nonvolatile memory, a vehicle manufacturer cannot perform diagnosis and analysis for failure. In order to avoid such an erroneous operation, there are related art techniques such as a memory rewritten system which performs certification using a security function. Such a security function is stored in both the vehicle control device and a rewriting device. The vehicle control device calculates the security function, and the rewriting device also calculate the security function during the inspection work, and an inspector reads/rewrites information data out/into the built-in nonvolatile memory only when both of the calculation results agreed with each other. This means that a specially authorized or designed rewriting device (namely, a dedicated rewriting device) using a formal security function can allow to read out/rewrite the dialogue information from/into the nonvolatile memory. This can avoid carelessness or unexpected deletion.
However, such related art techniques involves a possibility of deleting the important dialogue information by wrong or erroneous operations under a condition where the specially designed rewriting device is equipped with such a built-in nonvolatile memory using the formal security function, and it is thereby impossible to completely prevent occurrence of such an erroneous deletion of the dialogue information stored in the nonvolatile memory. In addition, when vehicle manufacturers and dealers want to read out the dialogue information stored in the memory in the vehicle control device, it must be required for each of the vehicle manufacturers and dealers to have a specially designed rewriting device using a formal security function. This requires much labor and time increases the maintenance cost.